Rubble Piles

5/21/06 – 5/27/06

by C. Zaitz

I was in the hospital waiting for my husband to have his one-inch kidney stone removed when I saw a show about near Earth asteroids and the threat they pose to us. There are lots of asteroids out there in uncomfortably close orbits to Earth. Some of these miles-wide mountains could annihilate life on Earth if they collided with us. But not all asteroids are whole. Some are collections of smaller rocks held together by their flimsy gravity. It turns out that these are the most dangerous threats to us because of the difficulty of destroying or deflecting them.

I thought of the giant stone in my husband’s kidney. Doctors slid a tube into his kidney, used directed energy to break the stone up, collected the pulverized bits into a net and pulled it out of him. Those little fragments would have caused more pain passing in a few days than the whole stone had caused sitting in his kidney for the past few years. Then I thought about those rubble pile asteroids. They are like garage-sized buckshot and would possibly do even more damage than a lone asteroid. How can we prevent such a collection of rocks from hitting the Earth? We don’t have anything in place to deal with such a threat – no rockets ready to go explode or deflect the asteroids, and certainly no nets to collect the pieces of any giant rubble piles heading toward us.

The truth is that we haven’t even located all the near earth asteroids. So far only 60% of them have been mapped, and even known asteroids can change orbit or character. Over the past few weeks, astronomers have watched comet 73P/Schwassmann-Wachmann 3 disintegrate into more than 30 fragments as it flew by some 6 million miles from us. That’s about 30 times the distance from the Earth to the Moon. It was not a threat, but astronomers are convinced it’s a matter of time before another very large asteroid or comet finds us. I say “another” because it has happened in the past. The giant meteor crater in Arizona is proof that a falling rock can make a big hole in the Earth. About one hundred tons of interplanetary material fall onto the Earth on a daily basis.

It’s enough to give you the willies. NASA does have NEO, its Near Earth Object program. According to NASA’s website, http://neo.jpl.nasa.gov/, NASA has five different programs concentrating on looking for NEOs, and Japan and Italy are also keeping an eye on the sky. I didn’t get a warm cozy feeling from their website since they do not address any capability of stopping NEOs that might impact the Earth. Necessity is the mother of invention, and there has been no immediate threat to spur the invention of Earth-protecting programs. However, if we are to have a chance at destroying or deflecting large Earth-bound boulders in space, early detection and action is the key. I hope we don’t wait until we are between a rock and a hard place, excuse the pun.

If these thoughts keep you awake at night, you can pass the time by watching for lovely Venus and the thin waning crescent Moon before dawn on the 24th. After sunset you can find Mars, Saturn and Jupiter spangled across the sky from west to east.

Until next week, my friends, enjoy the view!